Disposable anode package

ABSTRACT

The disclosure describes a disposable anode package for use in mechanically rechargeable oxygen-depolarized metal-air batteries. The anode package includes a cellophane envelope which retains the flocculent discharged anode material. A pull tab at the top of the cellophane envelope allows the spent anode to be removed. Dependent on the thickness of the individual cells, nonreactive mesh or fiber separator materials are used to prevent the discharged flocculent matter from dropping to the bottom of the anode package.

D United States Patent 1151 3,645,794

Hamlen et a1; 1451 Feb. 29, 1972 [54] DISPOSABLE ANODE PACKAGE 2,719,87410/1955. Chapman ..l36/l47 [72] lnventorsz. Robert P. Hamlen, Scotia;Erwin G. sink Baum) p both of NY I v 73 Assignee: The United sum ofAmerica as Primary Examiner-Allen Curtis m by u secretary f he NavyAttorney-R. S. Sciascia, L. l. Shrago and R. K. Tendler [22] Filed: Feb.19, 1970 57 ABSTRACT PP 121645 The disclosure describes a disposableanode package for use i in mechanically rechargeable oxygen-depolarizedmetal-air 52 us. c1. 136/86 A bmerias- The amde Package includes a 51 1Int CL which retains the flocculent discharged anode material. A pull 584 F ld i tab at the top of the canophane envelope allows the spent 1 le0 Search 136/86 147 anode to be removed. Dependent on the thickness ofthe in- [56] References Cited dividual cells, nonreactive mesh or fiberseparator materials are used to prevent the discharged flocculent matterfrom UNITED STATES PATENTS dropping to the bottom of the anode package.

3,457,1l5 7/1969 Kent ..l36/86A 4 Claims, 5 Drawing Figures F/occalfnfMa/fer/a/ PATENTEnrasae I972 SHEET 2 OF 2 J. Egg- 1 INVENTORS DISPOSABLEANODE PACKAGE The invention described herein may be manufactured andused by or for the Government of the United States of America forgovernmental purposes without the payment of any royalties thereon ortherefor.

This invention relates to mechanically rechargeable primaryoxygen-depolarized batteries and, more particularly, to a disposableanode package which permits removal of a spent anode and reactionproducts. This package includes an envelope which encases flocculentmaterial formed at the anode and which prevents this material fromsinking to the bottom of the cell where it will wedge the anode betweenthe cathode walls. This envelope also serves as a separator whichprevents anode ions from migrating to the cathode. Dendrite formation isthus inhibited. In one configuratiomthe separator is composed of acellophane bag and spacing material placed between thebag wall and theanode to maintain the, position of the flocculent material adjacenttheplace on the anode where it is formed. Removal of the anode, flocculentmaterial, spacing material and envelope is accomplished by pulling up ona tab portion of the bag. I

Metal-air cells have been used both as primary and secondary orelectrically rechargeable batteries. Examples of these batteries areshown in U.S. Pat. Nos. 3,457,115 to C. E. Kent, issued July 22, 1969;3,436,270 to H. G. Oswin et al., issued Apr. 1, 1969; and 3,297,484 toL. W. Niedrach, issued Jan. 10, 1967. In the case of magnesium-airbatteries, those that use a magnesium anode, electrical recharging isimpractical due to the highly reactive nature of magnesium. Magnesiumairbatteries may, however, be mechanically recharged by removing the spentanode and replacing it with a fresh anode. Additional electrolyte,usually a saline solution, is then added to the cell to complete themechanical recharging process.

One of the major difficulties in mechanically recharging such a cell isthe physical removal of the anode from the cell. Design restraints onlight portable battery packs usually restrict cell thickness to thepoint that the spacing between the anode and the cathodes is on theorder of a few centimeters. When magnesium anodes are used with a saltwater electrolyte, magnesium hydroxide is produced which falls to thebottom of the cell. This wedges the anode between surrounding cathodes,causing the cell to rupture and making removal of the anode difficult incells which are physically thin. In addition, flocculent materialeventually will block off the operative surface of the anode as it fallsto the bottom of the cell and will compact at the bottom of the cell tosuch an extent that electrolyte will be prevented from contacting themagnesium in the anode. This magnesium hydroxide must be removed priorto recharging to permit insertion of another anode as well as to preventobscuring of the anode by the compacted flocculent material.

The subject invention contemplates encasing the anode in a cellophaneenvelope which will permit the flow of electrolyte through its wallswhile at the same time containing the flocculent material. When theanode is removed by extracting the cellophane bag, both the spent anodeand the magnesium hydroxide are removed from the cell.

In addition, as part of the subject system, an expanded nonreactive meshor fiber separator is used in combination with the cellophane bag tomaintain this material at the place where it is generated so thatcompacting cannot occur. This permits the electrolyte to reach theanode. In the case of the fiber separator, capillary action also ensuresthat the electrolyte will be evenly distributed over the entire surfaceof the anode.

It is therefore an object of this invention to provide the anode of ametal-air cell with a microporous wettable envelope which has ahigh-electrolytic conductivity when wetted with the electrolyte used inthe battery.

It is a further object of this invention to provide means for containingflocculent material formed at the anode of a metalair battery and forremoving the anode and flocculent material when the anode is spent.

It is another object of this invention to provide the combination of abattery separator envelope and a flocculent material holding spacer forthe anode of a mechanically rechargeable metal-air battery cell.

It is still another object of this invention to provide a disposableanode package for use in mechanically rechargeable metal-air batterycells which includes a metal anode, a baglike separator with a pull tab,and spacing material between the anode and the separator.

Other objects, advantages and novel features of the invention willbecome apparent from the following detailed description thereof whenconsidered in conjunction with the accompanying drawings in which likenumerals represent like parts throughout and wherein:

FIG. 1 is a diagram of a metal-air battery anode with an expanded rayonmesh spacer and cellophane separator bag;

FIG. 2 is a diagram of a metal-air battery anode with a fiber spacer andcellophane separator bag;

FIG. 3 is a cross section of a metal-air cell in which a bagged anodehas been inserted showing the collection of flocculent material at thebottom of the separator envelope;

FIG. 4 is a partial cross section of a metal-air cell anode andseparator showing flocculent material held in place by a spacer; and

FIG. 5 is a cut away diagram of a metal air battery showing the positionof the anode package in an individual cell as well as a series of cellswhich, when wired in series, completes the battery.

Referring to FIGS. 1 and 2, anode plates 1 and connector clips 2 areshown encased in cellophane envelopes or bags 3 which have pull tabs 4appearing at the top in back of the anode. The front portions ofenvelopes 3 terminate below the level of electrolyte at edges 5. Thewall portions of the envelopes are sealed in any convenient manner withthe exception that holes 6 are left in the bottom of the bags to permithydrostatic pressure of the electrolyte on either side of the envelopesto equilibrate. This pressure occurs once these anode packages areinserted into a cell shown in FIG. 3 and the electrolyte is added to thecell. These holes are, however, sufficiently small to prevent flocculentmaterial from falling through. In one operative embodiment, holes havinga mean diameter of one-eighth inch were used. It will be appreciatedthat these holes may also be located on the sides of the envelope aswell as at the bottom for rapid equilibration. Clips 2,

in the configuration shown, protrude over edges 5 of the envelopes inany manner which will enable a solid contact with the cathode connectorof the next .cell in a cell series or with a terminal connection (notshown). In one embodiment, the anode is made of a flat sheet ofmagnesium to which clips 2 are bonded.

It will be appreciated that this envelope will be effective in anymechanically rechargeable metal-air battery cell in which flocculentmaterial, sometimes called sludge, is produced. The

envelope may be made from any material which is microporous and wettablewith a high-electrolytic conductivity when wetted with the electrolyteused in the battery. The material must not react with the activeconstituents of the battery and must have enough structural stability toprevent rupture when the anode package is removed. Cellophane sausagecasing, such as that manufactured by Union Carbide, which has beendeglycerinated and which contains only small amounts of sulfur hasproved satisfactory. Radiation grafted polyethylene which has beentreated so that it is wettable, swellable and microporous is alsoacceptable for use as an envelope. In general, any battery gradecellophane having -a thickness of one or two mils, whether glycerinatedor not, will be acceptable material for the envelope.

In FIG. 1, a spacing material of an expanded rayon mesh 8 is shown. Thismesh may be made of any nonreactive material such as polyethylene andfunctions to hold any flocculent material produced by the anode inplace. It also serves as a damping mechanism to the sloshing ofelectrolyte within the envelope. In FIG. 2, the separating material 9 isfibrous which,

in addition to holding flocculent material, also serves as a wick tobring electrolyte into contact with the anode as can be seen in FIG. 3,no spacing material need be used in the envelope. In this case, theenvelope serves its primary function of providing an efficient method ofremoving sludge and anode from the battery cell.

FIG. 3 is a cross-sectional view of a complete metal-air cell. Hereanode 1 encased by envelope 3 is shown inserted into a cell composed ofair cathodes supported by rigid metal casing members 11. The air cathodestructure is shown and explained in US. Pat. No. 3,297,489 to L. W.Niedrach, issued Jan. 10, 1967. These cathodes are generally amicroporous material which will maintain electrolyte on one side whilepermitting a gas to come through from the other side to react with theelectrolyte. More basically, the cathode must be nonwettable and providea catalyst to the oxygen in the air. The most common air cathodematerials are platinum,'palladium, silver and some types of activatedcarbon plated on a cathode matrix of stainless steel, nickel mesh or anymaterial that will not react with the electrolyte at a high rate. Poresize in the cathode is in the hundred to thousand micron range. Thecathode is usually made by bonding a mixture of Teflon and metal powdersto the screen to provide bonding and nonwettability. Connector clip 2extends beyond the cell casing and rests on a rubber insulating capmember 13 which is slotted to receive the anode and envelope and whichlimits the insertion of the anode so that it will not contact casingmember 11. When fully inserted, clip 2 also extends beyond envelope 3.Female connector 12 is shown mounted on the casing and is configured toreceive the anode connector clip from another cell. The battery is shownfilled with a salt water electrolyte 14 to a level above envelope edge5. Flocculent material 15, which in this case is magnesium hydroxide, isshown at the bottom of the envelope. In the embodiment shown in FIG. 3,no spacing material is used.

Removal of the anode and flocculent material is accomplished by pullingon tab 4. In addition to aiding in the removal of the sludge produced,it prevents magnesium ions and hydrogen produced in the reaction processfrom reaching the cathodes.

FIG. 4 is a cross-sectional view of a portion of the metal anode l, theenvelope 3, expanded rayon mesh 8 and flocculent material 15. Theaddition of the mesh to the cell shown in FIG. 3 prevents the flocculentmaterial from compacting at the bottom of the envelope, thus obscuring aportion of the anode. When the flocculent material is caught in themesh, it is not sufficiently dense to block the electrolyte fromreaching the anode. A like effect can be obtained with theaforementioned fibrous spacing material.

FIG. 5 is a cut away diagram of a partially completed metalair batterymade up of serially connected metal-air cells 21. Cell 210 is cut awayto show the insertion of removable anode package 22. In order tomechanically recharge the battery, spent anodes are removed by pullingthe tab on the envelopes and new anodes inserted as shown at 21a.Electrolyte is then added to each cell. This recharging process requireslittle or no skill, no danger to personnel and may be accomplished inthe most remote of locations. If the metal-air cell utilizes a magnesiumanode, it may be recharged by dipping the entire battery with new anodepackages in salt water.

This invention is not, however, limited to magnesium-air batteries.Disposable anode packages of the type described may be used to advantagein mechanically rechargeable cells whenever anodes are to be removed orwhenever flocculent sludge is produced at the anode-electrolyteinterface.

What is claimed is:

1. Apparatus for containing and removing flocculent lophane envelopesurrounding and spaced from said anode at its side and bottom portionsand having a tab portion formed as an extension of one of the sideportions of said envelope, said tab portion projecting above said anodeto facilitate removal of said envelope and anode such that whenever saidanodeis in its operating position within any of said cells it may beremoved by means of said tab portion, whereby any flocculent materialformed at the anode-electrolyte interface is contained within saidenvelope and is removed with the removal of said envelope and anode, thebottom portion of said envelope having openings of a size sufficient topermit said electrolyte to rapidly enter and small enough to preventsaid flocculent material from passing therethrough; and a nonreactiveseparator placed between said anode and the interior wall portions ofsaid envelope to maintain said flocculent material in the position atwhich it is formed on the surface of said anode,

whereby any flocculent material formed at the anode-electrolyteinterface is contained within said envelope and is removed with theremoval of said envelope and anode, and the electrolyte in each of saidcells is allowed to equilibrate on both sides of the wall portions ofthe envelopes inserted in said cells.

2. The apparatus as recited in claim 1 wherein said separator is anexpanded rayon mesh.

3. The apparatus as recited in claim 2 wherein said separator is formedfrom fibrous cellulosic material.

4. In an oxygen-depolarized metal-air cell of the type wherein a metalanode is inserted in an open-ended cavity formed by a gas-permeable aircathode and wherein an electrolyte is added to said cavity, a disposableanode package for use in mechanically recharging said cell comprising:

a highly reactive metal anode adapted to fit within said cavity; and

an electrolyte-wettable nonreactive microporous cellophane envelopesurrounding the side and bottom portions of said anode and having a tabportion integrally formed therewith as an extension of one of the sideportions of said envelope, said tab portion extending above the topportion of said anode and protruding through the open end of said cavityto facilitate removal of said anode and envelope from said cell whensaid anode is spent,

said envelope having openings at the bottom portion thereof of a sizesufficient to permit the electrolyte carried within said cell to rapidlyenter said envelope and small enough to prevent any flocculent materialformed at the anode-electrolyte interface from passing therethroughwhereby the electrolyte is allowed to equilibrate on both sides of thewall portions of said envelope, and wherein said disposable anodepackage further includes a nonreactive separator placed between saidanode and the interior wall portions of said envelope to maintain saidflocculent material in the position at which it is formed on the surfaceof said anode,

whereby any flocculent material formed at the anodeelectrolyte interfaceas a byproduct of the electromechanical reaction in said cell is removedwith the removal of said envelope and anode from said cell.

1. Apparatus for containing and removing flocculent material surroundingthe anode of a primary battery which is recharged by the removal of aspent anode therefrom and by the insertion of both a fresh anode andfresh electrolyte into each of the cells of said battery comprising: anelectrolyte-wettable nonreactive microporous cellophane envelopesurrounding and spaced from said anode at its side and bottom portionsand having a tab portion formed as an extension of one of the sideportions of said envelope, said tab portion projecting above said anodeto facilitate removal of said envelope and anode such that whenever saidanode is in its operating position within any of said cells it may beremoved by means of said tab portion, whereby any flocculent materialformed at the anode-electrolyte interface is contained within saidenvelope and is removed with the removal of said envelope and anode, thebottom portion of said envelope having openings of a size sufficient topermit said electrolyte to rapidly enter and small enough to preventsaid flocculent material from passing therethrough; and a nonreactiveseparator placed between said anode and the interior wall portions ofsaid envelope to maintain said flocculent material in the position atwhich it is formed on the surface of said anode, whereby any flocculentmaterial formed at the anode-electrolyte interface is contained withinsaid envelope and is removed with the removal of said envelope andanode, and the electrolyte in each of said cells is allowed toequilibrate on both sides of the wall portions of the envelopes insertedin said cells.
 2. The apparatus as recited in claim 1 wherein saidseparator is an expanded rayon mesh.
 3. The apparatus as recited inclaim 2 wherein said separator is formed from fibrous cellulosicmaterial.
 4. In an oxygen-depolarized metal-air cell of the type whereina metal anode is inserted in an open-ended cavity formed by agas-permeable air cathode and wherein an electrolyte is added to saidcavity, a disposable anode package for use in mechanically rechargingsaid cell comprising: a highly reactive metal anode adapted to fitwithin said cavity; and an electrolyte-wettable nonreactive microporouscellophane envelope surrounding the side and bottom portions of saidanode and having a tab portion integrally formed therewith as anextension of one of the side portions of said envelope, said tab portionextending above the top portion of said anode and protruding through theopen end of said cavity to facilitate removal of said anode and envelopefrom said cell when said anode is spent, said envelope having openingsat the bottom portion thereof of a sizE sufficient to permit theelectrolyte carried within said cell to rapidly enter said envelope andsmall enough to prevent any flocculent material formed at theanode-electrolyte interface from passing therethrough whereby theelectrolyte is allowed to equilibrate on both sides of the wall portionsof said envelope, and wherein said disposable anode package furtherincludes a nonreactive separator placed between said anode and theinterior wall portions of said envelope to maintain said flocculentmaterial in the position at which it is formed on the surface of saidanode, whereby any flocculent material formed at the anode-electrolyteinterface as a byproduct of the electromechanical reaction in said cellis removed with the removal of said envelope and anode from said cell.